The paper deals with the results of comparative experiments on the acoustic behaviour of the dolphin in the course of carrying out the task aimed at location of under-water targets in the natural acoustic environment and when exposed to man-made low-frequency interference. Thus, interference resistance of the dolphin sonar under in the complicated acoustic situation is provided by the following optimization mechanisms: pulse bursts (accumulation); varying frequency of pulse bursts (time selection); interval-time coding of bursts.